Axons and nerve terminals are unique subcellar structures of nervous tissue. Until recently, it was believed that all proteins of these neuronal subcellular compartments were synthesized in the nerve cell body and ultimately transported to their point of function. Our original findings derived from; 1) cell-free translation studies; 2) RNA-cDNA hybridization analysis; and 3) u(in situ) hybridization histochemistry indicated that the giant axon of squid contained small, but heterogeneous population of mRNA(Giuditta et al., 1986; Perrone Capano et al., 1987). It was estimated that this unique mRNA population contained approximately 100-200 different RNA sequences. During the past three years, direct evidence was obtained to demonstrate that the gain axon was capable of u(de novo) protein synthesis and contained biologically active polyribosomes, was judged by molecular biological and electron spectroscopic imaging techniques (Giuditta et al., 1991). Additionally, we have been successful in establishing a cDNA library encoding the axonal mRNA population using multiple cDNA library screening procedures and nucleic acid sequencing; 2) continue our investigation of the cellular origin of axonal mRNA by molecular biological analyses, u(in situ) hybridization histochemistry, and electron microscopy; and 3) test the hypotheses that axonal mRNA and polyribosomes are basic findings derived from this investigation may: 1) provide initial insights into the function(s) of this newly discovered unique mRNA population; 2) identify heretofore unknown neural-specific proteins; and 3) demonstrate the general occurrence and significance of axonal mRNA and polyribosomes.